Certain oxygenates such as formates are good fuel additive candidates as they have high octane properties, they can be produced from various hydrocarbon sources and can suppress pollutant emissions from vehicles. Consideration of methyl formate as a commercially viable additive for fuel blending would be favorable. Methyl formate is a good hydrocarbon fuel additive because it is an excellent gasoline blending component, having a research octane blending value, at 10 volume %, of 107 for regular gasoline and 116.5 for premium gasoline. Since formate is soluble in alcohol and ether it is a good oxygenated fuel additive and this is important since oxygenated fuels are becoming popular alternatives to hydrocarbon fuels. Other reasons why methyl formate would be a commercially desirable product are because it is colorless, flammable and agreeable in odor. However, serious attention to methyl formate as a commercially practical additive has been disfavored because of difficulties encountered in the synthesis.
U.S. Pat. No. 4,661,624 teaches synthesizing methyl formate from syngas, as a source of CO, and methanol over an alkali metal methoxide catalyst. The patent describes a solution to the pipe clogging and related manufacturing difficulties caused by a sodium methoxide catalyst precipitate which forms during methyl formate synthesis. In the described process a low product conversion is maintained so that higher concentrations of the catalyst can be used without the precipitation problem. The disadvantages of this approach include the low product conversion, an unrecycled syngas by-product and a need to restore the supply of pure methanol. The patent also teaches maintaining a low water content in the reaction zone which is, presumably, necessary to force complete reaction of methanol to methyl formate and because sodium methoxide decomposes in water. Because syngas has a high water content, driers for the syngas are an extra expense.
U.S. Pat. No. 4,661,623 teaches a method of making methyl formate from methanol and carbon monoxide using an anionic transition metal catalyst. Described is a high pressure synthesis using concentrated anhydrous methanol. Anhydrous methanol does not contain absorbed water.